American lawyers have been concerned for some time that the legally protected space for attorney-client communications is shrinking. But recent reports detailing massive electronic surveillance by the US government suggest truly confidential communications may largely be a thing of the past.

Documents leaked to the press over the past year by former NSA contractor Edward Snowden reveal that the US government is sweeping up vast amounts of private data and communications, including confidential information related to ongoing legal matters and privileged communications between attorneys and their clients.

In researching a new report over the past year, I interviewed over 40 attorneys and data security experts covering a range of legal practice areas to find out what impact, if any, these revelations have had on their work. Many expressed the concern that surveillance fears were undermining their ability to represent their clients effectively.

"I feel ethically obligated to tell all clients that I can't guarantee anything [they] say is privileged . . . or will remain confidential," a defense attorney specializing in national security and terrorism cases told me. Another has begun including a bolded auto-signature in her work-related emails: "Warning: Based on recent news reports, it is possible that the NSA is monitoring this communication."

A number of lawyers said that not being able to guarantee the privacy of their conversations makes it much harder to build trust with their clients, and makes clients less willing to speak fully and frankly, complicating efforts to devise an effective legal strategy. "If your clients see you uncomfortable communicating, they may resist telling you everything," observed one federal defender handling a terrorism case.

Some attorneys I spoke with are also nervous about falling short of their professional responsibilities to maintain confidentiality around their clients' information, which can include an explicit obligation to take positive steps to protect the confidentiality of information concerning their clients and cases. According to some experts in legal ethics, as the implications of large-scale surveillance sink in, unguarded use of conventional technologies for communicating with clients and storing information may become impermissible (if they haven't already).

In an effort to protect their communications and data, some attorneys have started changing their practices, turning to technologies like encryption, air-gapped computers isolated from the Internet and disposable "burner" phones. Another favorite technique is to use less technology, and trying to do more work face-to-face. One federal defender described meeting a client in person on the weekends to prepare a case—rather than communicating electronically during the workweek. As one prominent national security defense attorney, told me, summing up the changes: "Nobody practiced law like this 15 years ago unless you were a crook."

How effective any of these countermeasures are is hard to say, since there is still much we don't know about the nature and scope of US government surveillance.

Concerns are especially pronounced in contexts where the US government is an opposing legal party—and especially those where the government might have an elevated interest in the work of defense counsel, such as cases related to terrorism. As one prominent public interest lawyer put it, fear of government surveillance makes sense in part because the government that holds all of the surveillance information is also "the adversary we're worried about."

But the issue is not limited to the federal terror defense bar. Attorneys at corporate law firms may feel insulated from US surveillance, accustomed as those firms are to guarding against hacking by individuals or foreign governments. Yet a recent episode suggests that such confidence may be at least somewhat misplaced. Last February, the New York Times reported on the surveillance of attorneys at Mayer Brown, a major global law firm. While the attorneys were representing the government of Indonesia in a trade dispute with the US, Australian intelligence services picked up some of their communications with their client, and offered the results of that surveillance to the US.

NSA officials maintain that the agency is "firmly committed to the . . . bedrock legal principle of attorney-client privilege" and point to rules (called "minimization procedures") that are designed to limit the collection and use of privileged information. But the strongest known NSA rules for protecting privileged communications vacuumed up under Section 702 of FISA apply only to a limited subset of privileged communications (and not at all to confidential information more generally). Specifically, the rules apply to communications "between a person who is known to be under criminal indictment in the United States and an attorney who represents that individual in the matter under indictment...." Even there, the government can retain privileged communications even after recognizing they are privileged, and can make use of (broadly defined) "foreign intelligence information" that it gleans from those communications before realizing they should be specially protected. Some advocates worry that minimization procedures are even weaker for collection of information under other surveillance authorities, such as Executive Order 12,333.

A number of legal groups, including the American Bar Association, the New York City Bar Association, the National Association of Criminal Defense Lawyers and the National Lawyers Guild, have begun to wrestle with the issues raised by surveillance through outreach to government officials, amicus briefs, training webinars and reports.

But the legal community needs to do more. Legal organizations should band together and demand a full ban on the acquisition, retention, dissemination or use of protected attorney-client communications. We are all united by fidelity to the core values of the profession, which includes a long-standing recognition of the protections for the attorney-client relationship. Such values are essential to the right to counsel, and when they come under attack, we are all obliged to respond.

G. Alex Sinha is the Aryeh Neier Fellow at Human Rights Watch and the ACLU, and the author of "With Liberty to Monitor All," a new report on the impact of U.S. surveillance practices on journalists and lawyers.